The Rasmussen poll could be an outlier — most recent polls show Obama leading Romney nationally, and a number of polls in March showed the president stretching his lead to double digits.

The Real Clear Politics average of polls, which includes Thursday’s Rasmussen tie, shows the president with a 5.3 percent lead.

However, when Romney’s primary GOP rival Rick Santorum pulled out of the race earlier this week, Republicans and Democrats alike marked the occasion as the beginning of the Obama-Romney general election.

If other national polls in the upcoming weeks also show the race tightening, it could be a sign that Republicans have taken to rallying around their presumptive nomine, for what most analysts believe will be a tight race that will be determined by a handful of critical battleground states.